OM does not have a netinstall-iso. We have hopes for that in the future when we can discontinue our current iso builder for a newer tool that @bero has been working on.
Edit: Maybe ROME server baremetal x86_64 image might work if ROME is what you seek? I do not know if that one is tested? (That image was built August 24 so it is current.)
I am not the expert of the server images that would be @bero. You could talk to people more knowedgeable about this, including perhaps those that have used the server images at OpenMandriva Chat.